U.S. patent number 6,535,581 [Application Number 09/871,085] was granted by the patent office on 2003-03-18 for bypass for telephone system splitter.
This patent grant is currently assigned to Mphase Technologies. Invention is credited to Michael Singaliese.
United States Patent |
6,535,581 |
Singaliese |
March 18, 2003 |
Bypass for telephone system splitter
Abstract
In a telephone communication system employing a lower spectral
band and a higher spectral band for communication of voice and
video, wherein the system includes a first line for carrying
signals at both the first and the second spectral bands and a
second line for carrying signals at only the second spectral band,
and wherein capacitors are employed for connection of the second
line to the first line for exclusion of DC at a signal splitter of
the communication system, the system has a bypass DC signal path
for an alternative connection of the second line to the first line
in substitution for the connection of the capacitors. The bypass
can be activated electronically and remotely to establish
conditions for the conduction of test of the signal carrying
lines.
Inventors: |
Singaliese; Michael (New
Canaan, CT) |
Assignee: |
Mphase Technologies (Norwalk,
CT)
|
Family
ID: |
25356691 |
Appl.
No.: |
09/871,085 |
Filed: |
May 31, 2001 |
Current U.S.
Class: |
379/29.01;
370/248; 370/251; 379/22.07; 379/9.06 |
Current CPC
Class: |
H04L
43/50 (20130101); H04M 1/24 (20130101); H04M
3/303 (20130101); H04M 3/323 (20130101); H04M
3/2209 (20130101); H04Q 2213/13039 (20130101); H04Q
2213/13092 (20130101); H04Q 2213/1316 (20130101); H04Q
2213/13213 (20130101) |
Current International
Class: |
H04M
1/24 (20060101); H04M 11/06 (20060101); H04L
12/26 (20060101); H04M 3/22 (20060101); H04M
3/28 (20060101); H04M 3/32 (20060101); H04M
001/24 (); H04M 003/08 (); H04M 003/22 () |
Field of
Search: |
;379/1.01,1.03,9,9.06,12,16,22,26.01,27.02,27.03,28,29.01,29.02,32.02,22.07
;370/241,242,248,247,251 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Tieu; Binh
Attorney, Agent or Firm: Perman & Green, LLP
Claims
What is claimed is:
1. In a telephone communication system having a telco
interconnecting a local phone customer to a long distance phone
customer and to an internet service provider, the communication
system employing a first spectral band and a second spectral band
for communication of signals, wherein the first spectral band is
lower in frequency than the second spectral band, the upper edge of
the first band being lower in frequency than the lower edge of the
second band, and wherein the system includes multiple communication
channels of which each channel has a first line for carrying
signals at both the first and the second spectral bands and a
second line for carrying signals at only the second spectral band,
and wherein capacitors are employed at the telco in each of said
channels for connection of the second line to the first line for
exclusion of DC at a signal splitter of the communication system,
the signal splitter being located at the telco, the improvement
wherein the system further comprises, for each of said channels, a
bypass DC signal path for an alternative connection of the second
line to the first line in substitution for the connection of the
capacitors; an activation circuit for activating the bypass signal
path to bypass the capacitors; wherein the activation circuit
includes timing means for establishing an interval of time in which
the bypass is active, the interval of time being sufficiently long
to accomplish a testing of the first and the second lines with DC
connection between the first and the second lines; and the
activation circuit includes a receiver of a command signal, the
receiver serving to trigger operation of the activation circuit to
initiate the time interval in response to receipt of the command
signal.
2. A system according to claim 1 wherein the command signal is
transmitted along said second line, and said receiver includes a
filter tuned to receive the command signal to the exclusion of
signals in the first and the second spectral bands.
3. A system according to claim 1 wherein the command signal is a
first command signal, and said activation circuit further comprises
logic means which terminates the time interval upon receipt of a
further command signal prior to expiration of the time
interval.
4. A system according to claim 3 wherein the further command signal
is identical to the first command signal.
5. A system going to claim 1 wherein said bypass path is located
between said first line and said second line, and said activation
circuit includes a switch operative to connect said first line to
said second line to provide said bypass path.
6. A system going to claim 1 wherein said bypass path is located
between said first line and said second line, and said activation
circuit includes a switch operative to connect alternatively said
second line to said capacitors in the absence of said bypass path
and to said first line to accomplish said bypass path.
7. A system going to claim 1 wherein said bypass path is located
between said first line and said second line, and said activation
circuit includes a switch operative to connect alternatively said
first line to said capacitors in the absence of said bypass path
and to said second line to accomplish said bypass path.
8. A system according to claim 1 wherein the command signal is
transmitted as a radiant signal, and said receiver includes a
transducer for converting the radiant signal to an electrical
signal.
9. A system according to claim 8 wherein the radiant signal is
coded to identify a specific one of said communication channels,
each of said multiple channels includes an activation circuit
having a receiver identical to the receiver of the activation
circuit for a first one of said channels, all of said activation
circuits include decoders for monitoring a radiant signal as
received by the receivers of corresponding ones of said activation
circuits, and a bypass signal path is established for one of said
channels corresponding to an identification of channel made by one
of said decoders.
Description
BACKGROUND OF THE INVENTION
This invention relates to telephone communication equipment and,
more particularly, to a compact configuration of circuitry employed
in separation of video/data signals and voice signals in the
central office of a telephone company (telco) and, more
particularly, to an electronically activated bypass of a POTS
splitter to enable testing of a DSL line.
Telephonic communication among homes, businesses, and other
facilities is accomplished in well-known fashion via one or more
central offices of a telephone company with the electrical signals
being communicated via pairs (twisted pairs) of electrically
conducting wires. Voice signals are transmitted in a frequency band
of a few kilohertz (kHz), typically 0-4 kHz, wherein the twisted
wire pair can carry signals ranging from DC (direct current) to the
high frequency cutoff of the transmission circuitry. For normal
voice signal transmission, the high frequency cutoff is in the
range of approximately 3-4 kHz. However, the twisted wire pair is
capable of transmission of electrical signals of higher frequency,
suitable for computer modem digital communication, and for
compressed video signals such as video signals transmitted in the
MPEG-2 format, wherein a DSL frequency band of 30 kHz to 1104 kHz
(kilohertz) is available for these signals. Unlike transmission of
such signals by coaxial cable and by satellites wherein the signals
are modulated onto carriers, in the transmission of the signals via
the twisted wire pair there is no use of a carrier and the signals
are transmitted in their baseband format. As a result, there is
considerable interest in the use of telephone lines of the telco
for communication of high-speed modem signals and compressed video
signals in addition to voice signals among the homes, businesses,
and other facilities who are the telephone subscribers.
In communication, via the telephone lines, of the combined signals
of voice plus video, or other higher frequency signals such as the
high speed data transmitted by modem signals, the fidelity of the
voice signal is enhanced by separating the voice signal from the
high frequency signals. Voice circuitry, such as transmitter and
receiver, is employed for handling the voice communication, and DSL
(digital subscriber line) circuitry is employed for handling the
video and the data. At the telco and at the subscriber premises,
the voice and the video are handled separately by the voice and DSL
circuits, while between telco and the subscriber premises, both
voice and video are communicated by a common twisted pair.
In the telco, a low pass filter is provided for each of the
circuits to separate the voice from the DSL so that the voice can
be transmitted over long distance lines without interference from
the higher frequency signals of the DSL channel. The telco may be
provided with numerous racks of cards containing the low-pass
filters to provide the splitting of the DSL signals from the voice
signals, this portion of the telco being referred to as the POTS
splitter. An aspect in the construction of the circuitry at the
POTS splitter is the use of a capacitive connection of the DSL line
to the voice line to enable the aforementioned twisted pair to
carry both the voice and the DSL or video signals from the telco to
the subscriber premises, while the capacitive coupling prevents DC
on the twisted pair from being communicated to the DSL
circuitry.
There are times when it may be necessary to test the integrity of
the line carrying the DSL signal through the telco to the
subscriber premises. To conduct such a test, it is necessary to
provide a DC connection through the POTS splitter. In addition, the
test is conducted by injection of a test signal into the DSL line,
and measuring reflections of the signal. With presently available
equipment, there is an inconvenience in the conduction of such a
test because it is necessary to enter the POTS splitter portion of
the telco to provide a DC bypass around the capacitors which
connect the DSL line to the voice line. This inconvenience
represents a problem because of the need for additional personnel
and additional time in the conduct of the test procedure.
SUMMARY OF THE INVENTION
The aforementioned problem is overcome and other advantages are
provided, in accordance with the invention, by a construction of a
bypass circuit which bypasses the capacitive connection of a DSL
line to a voice line via a DC connection, and wherein the invention
provides also for a remote activation of the bypass circuit, so as
to enable conduction of the test procedure without requiring
personnel to enter into the POTS splitter to handle the numerous
racks of circuit cards for effecting the DC bypass during the test
procedure. A separate bypass circuit is provided for connection of
a DSL line to a voice line.
The bypass is accomplished by means of an electronically activated
switch, or relay, which provides a DC path through the POTS
splitter from the DSL port to the port which exits to the
subscriber premises, the DC path bypassing the terminals of the
capacitors which serve to connect the DSL line to the subscriber
twisted pair line. Between the DSL signal source and the POTS
splitter, there is provided a port for administration of the test
signal, and also a port for administration of a bypass-switch
activation signal. The invention includes a circuit which detects
the switch activation signal, and in response to the switch
activation, drives the switch from the normal switch position to
the bypass position. The circuit includes a bandpass filter having
a passband that selects the activation signal from among other
signals which may be present, such as a voice signal or a video
signal. The foregoing ports to the DSL line and the switch driver
circuit allow personnel to operate from a location outside the POTS
splitter to operate the bypass and to conduct a test of the DSL
channel.
BRIEF DESCRIPTION OF THE DRAWING
The aforementioned aspects and other features of the invention are
explained in the following description, taken in connection with
the accompanying drawing figures wherein:
FIG. 1 shows diagrammatically electric circuitry of a telephonic
communication system, including a remotely activated DC bypass in a
POTS splitter in the telco, in accordance with the invention;
FIG. 2 is an electrical schematic diagram of circuitry of a
bandpass filter, a detector of a bypass activation signal, and a
driver of a bypass switch for the POTS splitter of FIG. 1;
FIGS. 3, 4, and 5 show different embodiments of a bypass switching
circuit employing the switch of FIG. 2; and
FIG. 6 presents a fragmentary diagrammatic view of a communication
system wherein a bypass is implemented by command from a radiated
signal in accordance with an alternative embodiment of the
invention.
Identically labeled elements appearing in different ones of the
figures refer to the same element but may not be referenced in the
description for all figures.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows diagrammatically interconnections among components of
a telephone communication system 20, including central office
switching equipment 22, a POTS splitter 24, a bypass 26 for the
POTS splitter, and a main distribution frame 28 which are part of a
telco 30. For convenience in the description of the invention, a
single subscriber circuit is shown in the figure, it being
understood that many circuits are handled by the telco with the aid
of the switching equipment 22, and that connection to each of many
local telephone customers is provided via the main distribution
frame 28 of the telco 30. Also shown is a long distance phone line
32 carried by a telephone pole 34 for connecting between a long
distance phone customer 36 and the switching equipment 22. A
further phone line 38 carried by a telephone pole 40 connects the
premises of a local customer 42 to the main distribution frame 28.
A DSL line 44 connects an Internet Service Provider 46 via a DSL
modem 48 to a DSL port 50 of the telco 30. The DSL port 50 connects
via the POTS splitter 24 and the bypass 26 to a line port 52 which,
in turn, connects with the distribution frame 28.
The POTS splitter 24 comprises a low-pass filter 54, and a pair of
capacitors 56 and 58 that connect with a switch 60 of the bypass
26. The low-pass filter 54 connects from circuitry of the switch 60
and the capacitors 56, 58 via a PSTN port 62 to the switching
equipment 22. The capacitors 56, 58 protect the DSL line 44 from DC
voltage at the line port 52 and the PSTN port 62. A typical value
of capacitance for each of the capacitors 56 and 58 is 0.12 uF
(microfarads). The DSL line 44 has a port 64 whereby access is had
for application of a test signal and for measurement of reflected
signals on the DSL line by test equipment 66. The DSL line has a
further port 68 for application of a signal by a generator 70 to
activate the bypass switch 60. To facilitate the description of the
invention, the signal generator 70 is shown separately from the
test equipment 66, it being understood that, in practice, the
signal generator 70 may be incorporated within the test equipment
66. Also, if desired, the test equipment 66 can be incorporated
within equipment providing the DSL modem 48, thereby to reduce the
number of separate components of the communication system 20. Such
combination of equipment is simply a matter of convenience in the
building of the communication system 20, and does not affect the
practice of the invention.
The bypass 26 further comprises a bandpass filter 72, a detector
74, and a driver 76 for activation of the switch 60. For
convenience in describing the circuitry of the POTS splitter 24 and
its bypass 26, each of the signal-carrying lines 32, 38 and 44 are
shown as having two conductors as they pass their respective ports
62, 52 and 50 to connect with the POTS splitter 24. The premises of
the customer 42 has circuitry such as a modem 78 for receiving (and
transmitting) video/data signals present in the DSL frequency band,
a low-pass filter 80 which separates the high frequency signals
from the voice signals, and a telephone 82 for reception (and
transmission) of voice signals via the filter 80.
In the operation of the system 20, voice signals carried by the
lines 32 and 38 pass through the low-pass filter 54. However, the
relatively high frequency band of the signals on the DSL line 44
places these signals outside the passband of the filter 54, so that
these signals are excluded by the filter 54 from the long distance
phone line 32. The signals in the DSL frequency band are coupled
from the DSL line 44 to the local subscriber line 38 by the
capacitors 56 and 58, during normal operation of the system 20, but
are coupled to the subscriber line 38 by a DC connection of the
switch 60 during a test mode of the system 20. The testing is
accomplished by the test equipment 66 which applies a test signal
to sound out the lines 44 and 38 which serve as a channel for
carrying the DSL signal from the modem 48 to the premises of the
customer 42. Prior to initiating the testing, the generator 70
applies to the DSL line 44 a switch-activation command signal which
is received via the bandpass filter 72 and detected by the detector
74. The switch-activation signal is a pulse having a duration of
approximately 20 ms (milliseconds) or longer, by way of example, as
may be required for activating the circuitry of the driver 76. Upon
detection of the switch-activation command signal, the detector 74
signals the driver 76 to operate the switch 60 to provide the DC
connection which bypasses the capacitors 56 and 58. Thereupon, the
testing can be commenced.
More specifically, the driver 76 includes timing circuitry, as will
be described in further detail with reference to FIG. 2, which, in
response to the presence of the switch-activation signal, initiates
a bypass interval having a length of 3.5 minutes during which
interval the capacitors 56 and 58 are bypassed. It is to be
understood that the duration of 3.5 minutes for the bypass interval
is presented by way of example, and that some other length of the
bypass interval, such as five or ten minutes may be employed by
operation of the timing circuitry to provide such interval. At the
end of the bypass interval, the bypass terminates and the
capacitors 56 and 58 are again performing their function of
coupling the DSL signal while isolating the DSL line 44 from direct
current of the subscriber phone line 38. The bypass interval can be
terminated earlier by reapplication of the switch-activation
command signal before expiration of the 3.5 minutes.
In the choice of a suitable format for the switch-activation
signal, in the preferred embodiment of the invention, a single
pulse modulated onto a carrier of 18.4 kHz is employed because this
value of frequency is midway between the upper edge of the voice
spectrum (4.0 kHz) and the lower edge of the DSL spectral band (30
kHz). A bandwidth which is readily implemented for the bandpass
filter 72 is 3.5 kHz, by way of example, which is more than
adequate to pass the pulse of the switch-activation signal, and
narrow enough to avoid any significant interference with the signal
bands. By way of alternative embodiments of the invention, it is
noted that a bandpass or high-pass filter with passband well above
the upper edge of the DSL band (1104 kHz) could also be used to
transmit the switch-activation signal, in which case, the pulse
would be modulated on a higher frequency carrier such as 4 MHz, by
way of example.
With reference to FIG. 2, the bandpass filter 72 comprises two
inductors L1a and L1b which are wound on a common core indicated at
line 84, preferably in toroidal form, with the coupling polarity of
the magnetic field indicated by dots 86. A capacitor C1 is
connected serially with the inductor L1a to form a lateral branch
of the ladder circuit of the filter 72, and a capacitor C2 is
connected serially with the inductor L1b to form a further lateral
branch of the ladder circuit. A capacitor C3 is connected in
parallel with an inductor L2 to form a transverse branch of the
ladder circuit connecting between the foregoing to lateral branches
at the capacitors C1 and C2. A series connection of an inductor L3a
with capacitor C4 form a third lateral branch connecting with the
transverse branch, and a series connection of an inductor L3b with
capacitor C5 forms a fourth lateral branch connecting with the
transverse branch. The two inductors L3a and L3b are wound on a
common core, preferably in toroidal form, with the coupling
polarity of the magnetic field being indicated by dots.
An input terminal pair 88 of the filter 72 is located at terminals
of the inductors L1a and L1b for connection with the DSL port 50
(FIG. 1). An output terminal pair 90 of the filter 72 is located at
terminals of the capacitors C4 and C5. The following values of the
components of the filter 72 are provided by way of example in the
construction of a suitable filter, it being understood that other
configurations of filters may also be employed. The inductances of
the inductors L1a and L1b are the same and are equal to 1.4 mH
(millihenries), the inductances of the inductors L3a and L3b are
the same and are equal to 1.4 mH, the capacitances of the
capacitors Cl and C2 are both equal to 0.027 uF, the capacitances
of the capacitors C4 and C5 are both equal to 0.033 uF, the
inductor L2 has an inductance of 160 uH (microhenries), and the
capacitor C3 has a capacitance of 0.47 uF. The series and the
parallel resonances of the various branches contribute to providing
the desired center frequency and bandwidth with the aforementioned
values.
The detector 74 connects with the output terminal pair 90 of the
filter 72. The detector 74 comprises a full-wave bridge of four
diodes D1, D2, D3 and D4, and a capacitor C6. The four diodes of
the bridge are connected for rectifying the alternating current of
the signal input to the filter 72, and then applying the resulting
direct current to charge the capacitor C6 to a voltage
approximately equal to the peak value of the signal input to the
filter 72. One terminal of the capacitor C6 next to ground at 92,
and the other terminal of the capacitor C6, which receives a
positive charge relative to ground, connects with the coil 94 of a
relay K1. The coil of the relay K1 is connected in parallel to the
capacitor C6. The positive terminal of the capacitor C6 also
connects to the drain terminal, D, of a transistor Q1, which is an
FET (field effect transistor), preferably a MOSFET. A source
terminal, S, of the transistor Q1 connects with a contact 96 of the
relay K1, and a gate terminal, G, of the transistor Q1 connects via
line 98 to a flip-flop FF1 of the driver 76. The source terminal of
the transistor Q1 connects with a circuit node having a voltage
potential identified as Vcc, which potential is applied to various
other points within the circuitry of FIG. 2.
During a state of deactivation of the relay coil 94, the contact 96
is open. Upon energization of the coil 94 with current from the
capacitor C6, the contact 96 closes to apply a power supply voltage
V+ to the source terminal of the transistor Q1 and to the node
having the voltage Vcc. Prior to a closure of the contact 96, as
the capacitor C6 builds up charge, there is sufficient voltage to
induce current flow within the transistor Q1 via a drain-to-source
diode internal to the transistor Q1. This current through the
transistor Q1 results in a relatively small positive value of
voltage at Vcc. Subsequently, as the voltage across the capacitor
C6 increases still further then, as noted above, the relay K1 is
activated to close the context 96, at which time the value of the
voltage Vcc increases further to V+.
The detector 74 comprises a second branch having a diode D5 which
connects to the output terminal pair 90 of the filter 72 at the
junction of diode D1 and capacitor C4. The second branch of the
detector 74 further comprises a capacitor C7 of which one terminal
is grounded and the second terminal connects via a resistor R1 with
a cathode of the diode D5. A resistor R2 is connected in parallel
to the capacitor C7. The second branch of the detector 74 further
comprises a transistor Q2, which is an FET having a grounded
source, and a gate terminal which connects to the junction of the
capacitor C7 with the resistor R1. A drain terminal of the
transistor Q2 connects via a resistor R3 to the circuit node of
potential Vcc. The drain terminal of the transistor Q2 also
connects via line 100 to an inverter 102 of the driver 76. The
second branch of the detector 74 functions as a half wave detector
wherein the diode D5 applies current to charge the capacitor C7.
The series arrangement of the resistors R1 and R2 acts as a voltage
divider which reduces the value of the voltage at the capacitor C7
as compared to the value of the voltage at the capacitor C6. The
presence of the detected voltage at the capacitor C7 is operative
to place the transistor Q2 in a state of conduction. Upon closure
of the relay contact 96, the voltage Vcc is equal to the voltage
V+, and current flows from drain to source in the transistor Q2. In
the absence of the voltage across the capacitor C7, the transistor
Q2 is in a state of nonconduction. The following component values
are employed in the detector 74, namely, C6 and C7 are both 1.0 uF,
and R1, R2, and R3 have values of 2 k, 20 k and 10 k ohms.
In the driver 76, the flip-flop FF1 and a further flip-flop FF2 are
constructed as a dual, type-D flip-flop integrated circuit. The
driver 76 further comprises a second inverter 104, and a timer 106,
wherein the timer 106 comprises a counter 108 and an oscillator
110. A frequency of oscillation of the oscillator 110 is set by use
of external resistors R4 and R5, and an external capacitor C8.
Power to the dual flip-flops FF1 and FF2 is provided by the voltage
Vcc, wherein the flip-flops FF1 and FF2 are connected between Vcc
and ground. A capacitor C9 is connected in parallel to the
flip-flops between Vcc and ground. Power to the timer 106 is also
provided by the Vcc, wherein the timer 106 is connected between Vcc
and ground with a capacitor C10 connected in parallel to the timer
106 between Vcc and ground.
The voltage level on line 112 is applied to both of the flip-flops
to clear their output values at their respective terminals Q to a
relatively low voltage of logic "0" during power-up of the
circuitry connected to Vcc. The voltage level on line 112 is
attained by connection of the line 112 via a diode D6 to Vcc, and
via a series connection of resistors R7 and R8 to Vcc. A capacitor
C11 connects between the junction of the resistors R7 and R8 to
ground. During power up, as Vcc increases, the capacitor C11 holds
the junction of the resistors R7 and R8 near ground potential, this
low potential holding the output terminals Q of the respective
flip-flops at logic 0. Subsequently, as the capacitor C11 slowly
charges, and the voltage level at line 112 rises, voltage levels of
the signal lines within the driver 76 and the detector 74 have
stabilized, and the flip-flops FF1 and FF2 can be operated
normally. The diode D6 is back biased against the potential Vcc to
provide a safety function of draining the charge of the capacitor
C11 upon de-energization of the circuitry so as to protect the
flip-flop from the high-voltage of the capacitor.
The driver 76 further comprises a transistor Q3, which is an FET,
preferably a MOSFET, for operating the switch 60 (FIG. 1) which is
implemented in the circuitry of FIG. 2 by means of a relay K2. A
gate terminal of the transistor Q3 is connected to the output
terminal Q of the flip-flop FF2 via the serial connection of a
resistor R6 and a diode D7, and wherein a parallel combination of a
resistor R9 and a capacitor C12 connects between the gate terminal
and ground. The relatively high-voltage of the logic-1 state at the
output terminal Q of the flip-flop FF2 feeds current through the
resistor R6 and the diode D7 to the gate of the transistor Q3 to
place the transistor Q3 in May state of conduction. The current in
the transistor Q3 flows through a coil 114 of the relay K2 to
operate the contacts of the relay K2 to provide various closures
and openings of the contacts for bypassing the capacitors 56 and 58
of the splitter 24 (FIG. 1). The following component values are
employed, namely, R4 and R5 are both 120 k ohms, and C8 is 0.2 uF.
The resistors R6, R7, R8 and R9 are 50 k, 1 k, 50 k and 250 k ohms,
respectively. The capacitors C9, C10, C11 and C12 are 1.0 uF, 4,7
uF, 1.0 uF and 4.7 uF.
In operation the circuitry of the driver 76 provides logic
functions in conjunction with the operation of the detector 74. The
counter 108 is reset (R) by a signal outputted by the first
inverter 102. The counter outputs a signal at terminal Q which is
applied to a preset terminal of the flip-flop FF1. The preset
terminal and the D terminal of the flip-flop FF2 are connected to
Vcc. The output terminal Q of the flip-flop FF2 is connected also
to the D terminal of the flip-flop FF1. The output terminal Q of
the flip-flop FF1 drives, via the line 98, the gate of the
transistor Q1 to place the transistor Q1 in a state of conduction.
The signal outputted by the second inverter 104 is applied to the
clock inputs of both of the flip-flops FF1 and FF2.
In the dual flip-flops FF1 and FF2, both the preset and the clear
functions are enabled by a logic 0 which override the normal
function of transferring the logic level at the D input to the Q
output at 0-to-1 transitions of the clock input C. Upon turn-on of
power, the status of the output is desire to be a 0 at Q for both
of the flip-flops. This is accomplished by connection of the clear
line 112 to the capacitor C11 with the pull-up resistor to the Vcc
supply. This forces the outputs Q to a low level while the supply
and the clock inputs are still in transition. The low voltage level
at the capacitor C11 is retained until after conclusion of the
transitions in the supply and the clock inputs. Upon attainment of
the logic-1 voltage level, normal flip-flop operation is
enabled.
In the timer 106, the reset signal provided by the first inverter
102 is a logic 1, which sets the counter 108 to zero and stops the
oscillator 110. Upon termination of the reset, the counter 108
begins counting up to a preset value of maximum count. The Q output
of the counter 108 makes a transition from a logic 1 (high voltage)
to a logic 0 (low voltage) after a predetermined interval of time,
such as 3.5 minutes, has elapsed. The inverters 102 and 104 each
contain a Schmidt trigger input for improved reliability.
During normal operation of the telephone communication system 20,
the circuitry of FIG. 2 is de-energized. Upon detection of the
switch-activation signal by the detector 74, wherein the value of
the voltage Vcc begins to rise through action of the
drain-to-source internal diode of the transistor Q1, the various
capacitors and resistors being energized by the voltage Vcc begin
functioning as timing elements to prevent random logic status of
the active components upon the turn-on of power. After a period of
time, a standby status is reached.
The following sequence occurs during the period of time between the
initial Vcc rise and the standby status. The transistor Q2 turns on
when the voltage across capacitor C7 exceeds the gate-to-source
threshold of the transistor Q2. This places the timer 106 in its
reset mode, prevents a preset of the flip-flop FF1, and holds the
clock signal output from the inverter 104 at logic 0. Also, the
clear inputs to the flip-flops FF1 and FF2 transition from logic 0
to logic 1 after the capacitor C11 has charged to its full voltage,
leaving the Q outputs of the flip-flops FF1 and FF2 at logic 0;
transistor Q1 turns on. Transistor Q3, which was initially
de-energized before energization of the relay K1, remains in a
state of nonconduction because the Q output of flip-flop FF2 is at
logic 0 and the charging rate of capacitor C12 is sufficiently slow
to prevent possible turn-on transients at the Q output of the
flip-flop FF2 to have activated the transistor Q3.
The above-noted duration of the switch-activation signal inputted
to the bandpass filter 72 is sufficiently long to allow standby
status to be achieved. The standby status remains in effect until
the switch-activation signal terminates. Upon termination of the
switch-activation signal, the capacitors C6 and C7 of the detector
74 discharge, but the relay K1 is kept energized by operation of
the transistor Q1 which remains in a state of conduction for
providing current to the coil of the relay K1. As a result of the
discharging of the capacitor C7, there is a turning-off of the
transistor Q2. This results in a termination of the resetting mode
of the timer 106, and allows the counter 108 to begin counting
timing pulses produced by the oscillator 110. Also, there occurs a
0-to-1 transition at the clock (C) inputs to the flip-flops,
resulting in a logic 1 state at the Q output of the flip-flop FF2
where a logic 0 remaining at the Q output of the flip-flop FF1. The
transistor Q1 remains in its state of conduction, and the capacitor
C12 begins charging. When the voltage across the capacitor C12
reaches the gate-to-source threshold of the transistor Q3, the
transistor Q3 conducts current and energizes the coil of the relay
K2. Thereupon, the contacts of the relay K2 provide the bypass of
the splitter capacitors 56 and 58.
The bypass of the splitter capacitors 56 and 58 is retained by the
energized relay K2 until either the timer 106 has counted out the
aforementioned interval of 3.5 minutes, or until the relay K2 is
de-energized sooner by a further application of the
switch-activation signal to the bandpass filter 72. With respect to
termination of the bypass by a completion of the timing interval,
the output Q of the timer 106 transitions from a logic 1 to a logic
0 producing a preset of the flip-flop FF1. This change is the logic
level of the Q output of the flip-flop FF1 from a 0 to a 1 with a
resulting turning-off of the transistor Q1. Thereupon, the coil
current of the relay K1 terminates, and the charge on both of the
capacitors C9 and C10 decays until all components are turned off,
including the relay K2. Deactivation of the relay K2 terminates the
bypassing of the splitter capacitors 56 and 58.
In the event that the bypassing of the splitter capacitors 56 and
58 is terminated early by application of the further
switch-activation signal, the capacitor C7 of the detector 74 is
recharged to activate the transistor Q2. The signal outputted by
the transistor Q2 on line 100 terminates counting by the counter
108 by resetting the counter 108. The circuit remains in this state
until termination of the switch-activation signal in the bandpass
filter 72. Thereupon, the transistor Q2 turns off resulting in a
low-to-high transition of the clock inputs to the flip-flops FF1
and FF2. This changes a logic level at the Q output of the
flip-flop FF1 from a 0 to a 1. The transistor Q1 turns off with a
termination of the coil current of relay K1. It is noted that the
capacitor C6 discharges upon termination of the switch-activation
signal, and that the capacitors C9 and C10 discharge upon
deactivation of the relay K1. Thereupon, all of the components are
deactivated, including the relay K2 with resulting termination of
the bypassing of the splitter capacitors 56 and 58.
With reference to FIGS. 1, 3, 4 and 5, and is noted that the switch
60 of the bypass 26 provides for a connection of circuitry between
the three ports, namely the DSL port 50, the line port 52 and the
PSTN port 62 to accomplish the bypass function. FIG. 3 shows a
first configuration of the circuitry of the switch 60. Closure of
the contacts of the relay K2 provide a DC path between the DSL port
and the line port. The DC path bypasses the capacitors 56 and 58.
In the circuitry of FIG. 4, the contacts of the relay K2 provide
for an alternative connection of the DSL port to either the
capacitors 56 and 58 or to the line port. The alternative
connection accomplishes the bypass function. In the circuitry of
FIG. 5, the contacts of the relay K2 provide for an alternative
connection of the line port to either the capacitors 56 and 58 or
to the DSL port. The alternative connection accomplishes the bypass
function.
FIG. 6 shows a fragmentary view of FIG. 1 which is altered to show
an alternative embodiment of communication system 20A which differs
from the communication system 20 of FIG. 1 in that, instead of
making a direct connection to the DSL line 44 for transmitting and
receiving the bypass switch-activation command signal, the system
20A of FIG. 6 employs a signal generator 116 which drives a radiant
signal source 118. The signal generator includes a coding circuit
to output a coded signal for driving the radiant signal source 118.
By way of example, the radiant signal source 118 may be an acoustic
source radiating a sound at a high frequency (ultrasonic) outside
the range of audible sounds, or alternatively, an electromagnetic
signal such as an infrared or microwave signal. The coded signal
from the generator 116 amplitude modulates the signal radiated by
the source 118 so that a coded radiant signal is transmitted by the
source 118. The generator 116 and the radiant source 118 may be
combined in a single modular unit, similar to the remote controller
commonly used in homes for operation of a VCR (video cassette
recorder).
In the system 20A, each DSL line has its own set of splitter
capacitors 56 and 58, and its own splitter bypass 26A. Each DSL
line with its corresponding phone line 38 to the premises of a
customer 42 (FIG. 1), to which phone line the DSL line is coupled
by capacitors 56 and 58, may be regarded as a communication
channel. Each bypass 26A comprises a receiver 120 of the radiant
signal transmitted by the radiant source 118. In the case wherein
the radiant signal is an acoustic signal, the receiver may comprise
a microphone and an amplifier, wherein the microphone functions as
a transducer for converting the received sonic signal to an
electrical signal and the amplifier amplifies the electrical signal
to a suitable level for signal processing. By way of further
example, if the radiant signal is an infrared signal, the receiver
120 may comprise a photodetector which converts incident infrared
radiation to an electric signal. In the case of a microwave signal
radiated by the source 118, the receiver 120 may comprise a diode
detector of microwave energy for providing an electrical signal.
The electrical signal outputted by the receiver 120 is amplitude
modulated with the code provided by the generator 116. In
accordance with a feature of this embodiment of the invention, each
DSL line and its communication channel is provided with an
identifying code, and the corresponding bypass 26A is provided with
a decoder 122 connected to the receiver 120. The decoder 122 for
each bypass 26A is programmed to acknowledge receipt of a code
identifying the corresponding DSL line and its communication
channel to be tested.
In order to initiate testing of a specific one of the DSL lines at
the telco 30 (FIG. 1), the personnel conducting the test identify
the line at the generator 116 so as to output the corresponding
code. The decoders 122 associated with the various DSL lines are
nonresponsive to the received code except for the decoder 122 of
the identified DSL line, which decoder 122 acknowledges the command
for operation of the bypass 26A by outputting an acknowledgement
signal, such as a logic-1 signal. The logic-1 signal activates an
oscillator 124 to produce an oscillatory signal similar to that
outputted by the bandpass filter 72 (FIG. 1) to be received by the
detector 74, in the manner described above in the description of
the system 20 (FIG. 1). The logic-1 signal is a pulse signal having
the same duration as the switch-activation command signal described
above for the system 20. Therefore, the signal received by the
detector 74 in the system 20A is indistinguishable from the signal
received by the detector 74 in the system 20, and the detector 74,
the driver 76 and the switch 60 function to provide the bypass of
the capacitors 56 and 58 in the system 20A in the same manner as
was described above for the operation of these components in the
system 20.
It is to be understood that the above described embodiments of the
invention are illustrative only, and that modifications thereof may
occur to those skilled in the art. Accordingly, this invention is
not to be regarded as limited to the embodiments disclosed herein,
but is to be limited only as defined by the appended claims.
* * * * *